Dog Lobes Research Articles

Perivascular pressure measurements by wick-catheter technique in isolated dog lobes.

Saline-filled wick catheters were inserted intraparenchymally in the loose connective tissue separating the bronchus and pulmonary artery of unperfused isolated dog lobes. Px, the difference between perivascular pressure and pleural surface pressure (which was atmospheric pressure), was measured by the wick for arterial pressures (Pa) of 10 and 25 cmH2O at lobe transpulmonary pressures (Ptp) of 25, 15, 10, 5, and 2 cmH2O during a deflation pressure-volume maneuver. The response time of Px to step changes in Pa was relatively short, a pressure plateau always occurring in less than 3 min. For Pa of 25 cmH2O, mean Px in five lobes was -2 cmH2O at Ptp of 2 cmH2O and decreased almost linearly to -9 cmH2O at Ptp of 25 cmH2O. Reducing Pa from 25 to 10 cmH2O resulted in a mean decrease in Px of 1 cmH2O at Ptp of 2 cmH2O and 2 cmH2O at Ptp of 25 cmH2O. These results are generally consistent with predictions from a continuum-mechanics analysis of pulmonary vascular interdependence and do not support the concept that perivascular interstitial fluid pressure is different from surface pressure.

A continuum mechanics analysis of pulmonary vascular interdependence in isolated dog lobes

The pressure-diameter (PD) behavior of intact pulmonary vessels was measured roentgenographically at several fixed deflation transpulmonary pressures (Ptp). At any constant vascular pressure (Pv), the intact-vessel diameter was larger for higher Ptp. The behavior of the parenchyma was described by a nonlinear analysis. An excised-vessel PD behavior was computed which was consistent with both nonlinear parenchymal behavior and measured intact-vessel PD behavior. Estimates of Px', the difference between the perivascular pressure and the pleural pressure, as a function of Ptp and Pv were obtained. For physiological values of Pv, mean values of Px' for arteries were -1 cmH2O at Ptp of 4 cmH20 and decreased almost linearly to -15 cmH20 at Ptp of 25 cmH2O. Veins showed a similar behavior, but Px' was more positive. Increasing Pv raised Px' and decreasing Pv lowered Px' at all values of Ptp. These results indicate that the interdependence effect is small at functional residual capacity, increases with lung inflation, and is greater for arteries than veins.

INCREASED PANCREATIC LECITHINASE-A ACTIVITY AND ITS CORRELATION TO ALVEOLAR STABILITY DURING SHOCK

The objective of the present study was to investigate the role of pancreatic lecithinase-A released into systemic circulation during shock involving the deterioration of alveolar surface activity. Mongrel dogs were led to hemorrhagic shock maintaining mean arterial blood pressure 40 mmHg until 40% of shed blood was spontaneously taken up. Then remaining blood was retransfused and the experiment was terminated when arterial pressure declined to 50 mmHg. The changes of lecithinase-A and lysosomal hydrolases in the pancreas and plasma were observed every hour through the experement. Pulmonary surface activity was determined on excised lobes at the terminal stage after retransfusion. Next, the effect of lecithinase-A infused intraveously on arterial blood oxgenation and pulmonary stability was assessed on anesthetized dogs.The arterial blood oxygen tention decreased at the terminal stage following retransfusion in shocked animals. Plasma concentration of lecithinase-A increased markedly 120 minutes after the initiation of oligemic hypotention, being preceded by a rise in lecithin splitting enzyme of the pancreas. Pressure-volume curves of the excised lobes of dogs in hemorrhagic shock and lecithinase infusion showed significant shifts to the right, demonstrating the reduction in pulmonary surface activity. These results suggest that pancreatic lecithinase-A released into plasma may inactivates pulmonary surface active substances.

Peribronchial pressure in excised dog lungs.

To characterize the stresses which determine bronchial diameter in the lung, we estimated peribronchial pressure (Px) relative to intrabronchial pressure (Pbr) and to alveolar pressure (PA) for the main lobar bronchus of excised dog lobes using the technique of Takishima et al. (J. Appl. Physiol. 38: 875--881, 1975). The recoil of the bronchial wall, Pbr---Px, when smooth muscle was relaxed varied primarily with bronchial diameter. The recoil of the parenchyma around the bronchus, Px---Pa, varied with lung volume but was also diameter-dependent and served to double approximately the effective elastance of the bronchus in situ. We estimated recoils during slow deflations from TLC with the bronchus untreated, or pharmacologically contracted or relaxed. In untreated and relaxed states, local parenchymal and bronchial recoils were of similar magnitude to overall lung recoil (i.e., Px congruent to Ppl) except at high inflating pressure (PA -- Ppl = 30 cmH2O) where they were about half as great. With contraction, bronchial and local parenchymal recoils increased to as much as twice overall lung recoil. Contracted smooth muscle exerted a radial stress of 36+/-14 cmH2O at full lung inflation but much less during stepwise deflation.

Studies of Ventilation and Perfusion during Hypoventilation of the Left Lower Lobe in Dogs

Studies of Ventilation and Perfusion during Hypoventilation of the Left Lower Lobe in Dogs

Effect of parenchymal shear modulus and lung volume on bronchial pressure-diameter behavior.

A method that interrelates lung pressure-volume behavior, bronchial pressure-diameter behavior, and parenchymal shear modulus is presented. The method was used to predict changes in intraparenchymal bronchial diameter that occurred when lobe pressure-volume behavior and parenchymal shear modulus were markedly changed by inducing air trapping in isolated dog lobes. Predictions agreed with measurements, thereby supporting the general method. Measured values for the shear modulus were approximately 0.7 times the transpulmonary pressure for the control state. Estimated values for the peribronchial pressure difference from pleural pressure during a deflation pressure-volume maneuver for transpulmonary pressures below 12 cmH2O were small, approximately +/- 1 cmH2O, its sign being positive or negative, depending on whether the bronchus was dilated or contricted.

Elastic constants of trapped lung parenchyma.

Isolated dog lobes were maximally trapped with air, and their parenchymal elastic properties were measured at the trapped volume. Indentation tests were performed on the surface of the lobes, followed by uniaxial and torsion tests on excised pieces of parenchyma. Similar values for Young's modulus were obtained from the indentation and uniaxial tests. The values for the shear modulus from the torison tests also were consistent with Young's modulus measured by the other procedures. The indentation test provided an accurate estimate of Young's modulus or the shear modulus for trapped lobes, and the results suggest that it is a valid method for estimating these constants in nontrapped lobes.

Indentation of a Membrane on an Elastic Half Space

An analysis is presented of the deformation of a homogeneous isotropic elastic half space whose surface behavior departs from the classical due to the presence of a pretensed membrane or a material surface which exhibits surface tension. Two related problems are considered: the axisymmetric displacements caused by a uniform circular load and by a concentrated normal force. In contrast to the classical solution, the uniform load problem with surface tension is found to have a finite slope and zero shear stress over the entire boundary. The analysis is used to interpret data from indentation tests on inflated dog lobes and the mechanical properties of both the lung parenchyma and the surface membrane are obtained. The observed shape of the indented surface agrees well with the prediction of the analysis.

Finite-element analysis of the strain variations in excised lobe of canine lung

The excised right lower lobe of a 10-kg dog's lung was manually inflated to the total capacity and then deflated in a step-wise manner to record the three-dimensional displacements of small metallic markers, which were affixed to the pleural surface, by employing a computer-based biplane roentgen-videographic technique. The temporal and spatial changes of the strains in the lobe during deflation were determined by partitioning of the lobe into a finite number of tetrahedral regions. By taking the implanted markers as the vertices of the tetrahedrons and utilizing their changes in spatial coordinates, finite-element calculations of the strain variations in the lobe were performed. Sample results of strains are presented. It shows that except in the vicinity of one of the implanted markers, the normal strains are generally higher than the shearing strains in the deflating excised lobe.

Regional esophageal pressures with lobar obstruction in dogs.

The right lower lobes (RLL) of intact horizontal dogs were obstructed at FRC during spontaneous breathing and artificial ventilation (IPPB). At end inspiration, pressure within the RLL became less than tracheal pressure, and pressure in the lower esophagus declined to a greater extent than in the upper esophagus. Tidal pressure swings in the obstructed RLL were larger than in the esophagus during spontaneous breathing but smaller during IPPB implying that the elastic recoil of the RLL decreased during inspiration at the mediastinal side. All these changes were intensified during RLL atelectasis and counteracted by strapping of the lower chest wall. These results indicate that: (a) around a lobe moving out of phase with the rest of the lung, a force is created tending to minimize the lobar volume differences; (b) the obstructed lobe is deformed during inflation of the rest of the lung; (c) esophageal (and hence pleural) pressure gradient is modified by this localized intrapulmonary pathology apparently due to shape interactions between chest wall and lung.

Effect of vascular, pleural, and alveolar pressures on filtration in isolated, perfused lobes of dogs

The vascular pressure ( Pvas), pleural pressure ( Pl), and alveolar pressure ( Palv), play an important role in determining the state of the lung. In this paper, we vary these pressures systematically to measure their effect on the rate of weight gain of the isolated perfused lung. As the lung's lymphatic system was ligated, this rate is taken as the rate of transvascular filtration, J f. Designating the change in J f when Pvas alone is lowered by 8 cmH 2O as 100%, we found the change in J f when all pressures are increased by 8 cmH 2O is 0 ± 2% and that when Palv is raised from 8 to 14 cmH 2O is −2 ± 5%. These results, together with the linear dependence of J f on Pvas and Pl, yield this empirical equation: J f = K( Pvas − Pl − A) where K and A are constants. The correlation of this equation with the Starling equation on transvascular filtration and the comparison of the mechanical equilibrium of the membrane surrounding fluid cuffs in the interstitia of the lung and that of the pleural membrane identify K as the filtration coefficient. and the interstitial fluid pressure in the lung closely approximates the pleural pressure for lungs undergoing moderate edema. The transmission of the pleural pressure to the interstitial fluid space is due to the action of the lung tissue and the surface tension. A similar dependence of J f on Pvas, Pl, and the tracheal pressure is found for alveolar edema.

Influence of lung parenchyma on dynamic bronchial collapsibility of excised dog lungs.

The main bronchi of excised dog lobes were obstructed 5-6 cm from their origin with beads, so that they did not communicate with the peripheral air spaces. With the lobe held at constant transpulmonary pressure, bronchial pressure-volume curves were recorded during both static and dynamic bronchial deflations. This was done both before and after dissecting the obstructed bronchus free of parenchymal attachments. The parenchymal contribution on dynamic deflation was much larger than the airway contribution: dynamic bronchial compliances in intact bronchi were 58 +- 8% and 65 +- 8% of the static at dynamic rates of bronchial deflation of 14 and 8 ml/s, respectively, whereas in dissected bronchi they were 72 +- 9% and 78 +- 9%. These relationships were not influenced by changes of transpulmonary pressure applied to the lobar parenchyma. The parenchymal effect on dynamic bronchial compliance was analyzed in terms of parenchymal interdependence and bronchial stress adaptation. We concluded that the presence of lung parenchymal attachments significantly reduced dynamic bronchial collapsibility as compared to static collapsibility.

General Anesthetics and Regional Hypoxic Pulmonary Vasoconstriction

Administration of N2O, fluroxene and isoflurane to the left lower lobe (LLL) of dogs anesthetized with pentobarbital was previously shown to inhibit LLL hypoxic pulmonary vasoconstriction (HPV). Using the same experimental model, the present study examined the effect of whole-lung administration of N2O, fluroxene, isoflurane, halothane, and enflurane on left-lower-lobe HPV. Selective ventilation of the LLL with N2 alone caused blood flow to the lobe to decrease 53.3 +/- 3.0 per cent. Responses to LLL hypoxia were remeasured during administration of inhalation anesthetics at 1 and 2 MAC to both the LLL and the rest of the lung. Isoflurane and fluroxene progressively inhibited and at 2 MAC halved lobar HPV. N2O (one third MAC) caused slight but significant inhibition, while halothane and enflurane caused slight and nonsignificant changes in lobar HPV. These effects of whole-lung administration of anesthetics on HPV were almost identical to those obtained when the administration was confined to the test lobe alone. It is concluded that N2O, isoflurane, and fluroxene locally inhibit regional HPV and via this mechanism increase total venous admixture, while halothane and enflurane do not have this effect.

INFLUENCE OF PULMONARY VASCULAR PRESSURE ON BRONCHIAL COLLAPSIBILITY OF EXCISED DOG LUNGS

The main bronchi of excised dog lobes were obstructed with beads, 5 to 6 cm from their origin so that they did not communicate with the peripheral air spaces. Both pulmonary artery and vein were cannulated and both pulmonary vascular pressures were controlled. With the lobe held at constant transpulmonary pressure, bronchial pressure-volume curves were studied during acute pulmonary vascular engorgement. The bronchial compliance was reduced at higher vascular pressure and the effect of vascular engorgement on the bronchial collapsibility was larger at higher transpulmonary pressure: bronchial compliance at vascular pressure-40 cm H2O at transpulmonary pressure 20, 10, 5, and 0 cm H2O respectively. We concluded that vascular engorgement increased parenchymal radial traction to the bronchi when the bronchi reduced its diameter, although it appeared that vascular engorgement resulted in little change in the lung elastic recoil pressure.

Effect of increased static lung recoil on bronchial dimesions of excised lungs.

We measured bronchial diameters and lengths during static deflation and inflation in eight excised dog lobes before and after static lung recoil (Pst(L)) had been significantly increased by cooling the lobe for 48 h at 4 degrees C and ventilating it for 3 h. In control lobes, bronchial diameters were the same at any volume even though Pst(L) was different during inflation and deflation. These results agree with those of Hughes et al. (J. Appl. Physiol. 32: 25-35, 1972). However, when Pst(L) was increased, diameters at a given volume were significantly increased over control values; diameters at a given pressure were nearly the same as the controls. Therefore, under these conditions, bronchial diameter did not conform to lung volume. The ventilation process appeared to alter the circumferential elastic properties of the bronchi because diameters at all pressures were slightly larger after ventilation. Bronchial length-volume relationships were the same in both control and ventilated lobes. Thus, when Pst(L) was markedly increased, diameter corresponded best to lung recoil and length to lung volume.

Influence of lung parenchyma on collapsibility of dog bronchi.

In five excised dog lobes in the distended state, we inserted several small beads into the bronchi roughly at their third branches and glued them airtight to the bronchial wall with adhesive substance, except for one which was open and through which the entire lobe could be expanded via collateral channels. This permitted us to measure the volume-pressure behavior of bronchi at different fixed lung tensions. From differences in pressure-volume curves of both the bronchi in situ and the bronchi intact within the lung showed a remarkably greater resistance to collapsing that dissected bronchi, and this characteristic tended to be much more intense when lung tension was increased. Determinants of maximum expiratory flow were discussed with these findings.

Pulmonary vascular interdependence in excised dog lobes.

ArticlePulmonary vascular interdependence in excised dog lobes.J J Benjamin, P S Murtagh, D F Proctor, H A Menkes, and S PermuttJ J Benjamin, P S Murtagh, D F Proctor, H A Menkes, and S PermuttPublished Online:01 Dec 1974https://doi.org/10.1152/jappl.1974.37.6.887MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByRespiratory‐Cardiovascular Interactions During Mechanical Ventilation: Physiology and Clinical Implications26 April 2022The development of various forms of lung injury with increasing tidal volume in normal ratsRespiratory Physiology & Neurobiology, Vol. 274Lung Circulation15 March 2016Non-uniform central airways ventilation model based on vascular segmentationComputers in Biology and Medicine, Vol. 65Pulmonary HemodynamicsRelease the PressureAnnals of the American Thoracic Society, Vol. 11, No. 4Mechanical interactions between adjacent airways in the lungBaoshun Ma, and Jason H. T. Bates15 March 2014 | Journal of Applied Physiology, Vol. 116, No. 6Influence of parenchymal heterogeneity on airway-parenchymal interdependenceRespiratory Physiology & Neurobiology, Vol. 188, No. 2Ventilator-induced lung injury: historical perspectives and clinical implications23 July 2011 | Annals of Intensive Care, Vol. 1, No. 1Ventilator-Induced Lung InjuryVentilator-Induced Lung InjuryFlow and pressure distributions in vascular networks consisting of distensible vesselsGary S. Krenz, and Christopher A. Dawson1 June 2003 | American Journal of Physiology-Heart and Circulatory Physiology, Vol. 284, No. 6Relative roles of vascular and airspace pressures in ventilator-induced lung injuryCritical Care Medicine, Vol. 29, No. 8Mechanical dissociation of bronchi from parenchyma in the immature piglet lungAnthony L. Mansell, Allison L. McAteer, and Eben H. Oldmixon1 July 2000 | Journal of Applied Physiology, Vol. 89, No. 1Effects of Decreased Respiratory Frequency on Ventilator-induced Lung InjuryAmerican Journal of Respiratory and Critical Care Medicine, Vol. 161, No. 2Ventilator-induced Lung InjuryAmerican Journal of Respiratory and Critical Care Medicine, Vol. 157, No. 1HEMODYNAMICS AND POSITIVE END-EXPIRATORY PRESSURE IN CRITICALLY ILL PATIENTSCritical Care Clinics, Vol. 12, No. 4Maturation of interdependence between extra-alveolar arteries and lung parenchyma in piglets.Circulation Research, Vol. 71, No. 3Regional compliance and bronchial pressure-diameter relationships in excised pig lungsRespiration Physiology, Vol. 86, No. 1Pulmonary interstitial resistanceAnnals of Biomedical Engineering, Vol. 15, No. 2Collateral Flow1 January 2011Effect of circulatory mechanics on hydrostatic forces producing pulmonary edemaJournal of Critical Care, Vol. 1, No. 4Pulmonary Circulation1 January 2011Pulmonary Interstitial Spaces and Lymphatics1 January 2011Effect of lung surface tension on pulmonary vascular mechanics in excised dog lungsRespiration Physiology, Vol. 56, No. 1Pulmonary Function and Exercise TestingBlood Flow in the LungPulmonary Circulation1 January 2011Mechanical factors determining pulmonary interstitial fluid pressureLung, Vol. 160, No. 1Effect of transpulmonary pressure on blood-flow velocity in pulmonary microvesselsRespiration Physiology, Vol. 43, No. 1Effects of spontaneous respiration on canine left ventricular function.Circulation Research, Vol. 45, No. 6Elastic properties of lung parenchyma: The effect of pressure-volume hysteresis on the behavior of large blood vesselsJournal of Biomechanics, Vol. 12, No. 10Influence of hematocrit, blood gas tensions, and pH on pressure-flow relations in the isolated canine lung.Circulation Research, Vol. 37, No. 5VILI: Physiological EvidenceCellular response to mechanical stressUnderstanding the Mechanism of Ventilator-Induced Lung Injury More from this issue > Volume 37Issue 6December 1974Pages 887-94 https://doi.org/10.1152/jappl.1974.37.6.887PubMed4436220History Published online 1 December 1974 Published in print 1 December 1974 Metrics

Intrapulmonary gas mixing in excised dog lung lobes studied by simultaneous wash-out of two inert gases

To study the role played by stratified inhomogeneity in limiting alveolar gas exchange, simultaneous wash-out of He and SF 6 was measured in excised, unperfused lung lobes of small dogs (mean weight 10.7 kg). The tidal volume was varied at constant end-inspired volume and constant ventilation frequency. The wash-out kinetics was characterized by the breath number constant, v, equal to the number of breaths required for decreasing the initial gas concentration by the factor l/e ≈ O.37. The ratio V He/ v SF t was on the average less than 1.0, indicating that wash-out of He was more rapid than that of SF 6, and increased towards unity with increasing tidal volume. On the basis of a serial two-compartment lung model, the effective diffusional conductance between lung gas and tidal gas or “stratificational diffusing capacity”, Dstr, for He and SF 6 was calculated from the relationship between V He/ v SF 6 , tidal volume and end-inspired lung volume. The calculated Dstr values increased strongly with increasing depth of inspiration. When compared with the anatomical human lung model of Weibel, Dstr increased more than proportionally to the cross-sectional area of the airways at the interface between tidal and lung gas. For lung volume, tidal volume and frequency of normal breathing, Dstr for 0 2 was estimated at about O.41 mmol · min −1 · torr −1. This value is 4–8 times higher than estimates of the gas transfer Do 2 for the lung lobe and would give rise to 0; and CO; pressure differences of no more than 1 torr. But with low tidal volume and high respiratory frequency, such as observed in panting, airways stratification is expected to grow rapidly to levels exerting severely limiting effects on alveolar 0; and CO 2 exchange.

Life-sustaining canine hepatic autotransplants.

Partial hepatic autotransplantation of the left lobes in dogs was performed with hepatectomy of the remaining lobes at either a staged (group 1) or simultaneous (group 2) procedure. Direct portal flow was established in group 2 dogs only. Values of postoperative liver function tests returned toward normal rapidly in group 2 animals but were abnormal in group 1 dogs until resection of the right lobes, handicapped by arterial and bile duct ligation at the second stage. Technetium Tc 99m liver scans and arteriograms demonstrated increasing size of the autotransplants in both groups, but at autopsy two months later, the weights and histological patterns indicated greater regeneration in group 2 than in group 1 dogs. Life-sustaining capability of autotransplanted liver lobes was established in dogs. There are possible clinical applications of these results, especially in patients with extrahepatic bile duct cancer.

The action of carbon dioxide on constricted airways

1. In artificially ventilated open-chest cats and dogs ventilation with 5-15% CO(2) reversed the bronchoconstriction caused by drugs or by pulmonary artery occlusion. Total lung resistance, ;static' lung compliance, and intratracheal or intrabronchial pressure at constant pump stroke were measured.2. CO(2) reduced resistance and increased compliance of the lung during infusions of 5-hydroxytryptamine (5-HT), histamine and acetylcholine in cats. In dogs CO(2) reduced resistance during 5-HT infusions; it caused small reductions in intratracheal pressure but no significant change in resistance during infusions of histamine and acetylcholine. Even in cats CO(2) had a larger effect during 5-HT than during histamine and acetylcholine infusions.3. Occlusion of a pulmonary artery caused increases in resistance and decreases in compliance in the affected lobes of both cats and dogs. These changes were partly reversed by ventilation with high CO(2) mixtures.4. The bronchodilator action of CO(2) took place over a wide range of P(a, CO2) values (20-100 torr).